1. Field of the Invention
This invention relates, in general, to electrical inductive apparatus, such as a transformer, and more particularly to electrical inductive apparatus where the cooling is achieved by vaporization of a liquid dielectric applied to the heat producing members. It is known to those skilled in the art, that electrical inductive apparatus can be cooled by the vaporization of two phase fluids which have a boiling point within the normal operating temperature range of the device.
In the aforementioned vaporization cooling system, the vapor produced subsequently condenses and can be reapplied to the heat producing members. However, in order to adequately cool the electrical apparatus and minimize the amount of fluid utilized in the system, the liquid dielectric must be recirculated. This poses reliability problems since the most common means of circulating liquid requires a conventional mechanical pump which contains many moving parts.
2. Description of the Prior Art
Several means have been developed which improve reliability by eliminating the mechanical pump. One is a vapor push pump disclosed in U.S. Pat. Nos. 3,819,301 and 3,834,835. According to this method, the vaporization of the liquid dielectric within a housing creates a vapor pressure which pushes an equal volume of liquid up a delivery conduit for subsequent application of the heat produced member. The vapor push pump still contains several moving parts which, although smaller in number than those in a conventional mechanical pump, could still cause reliability problems.
In another method, disclosed in U.S. Pat. No. 2,845,472, pressure differences within the cooling system cause the vapor, created by the vaporization of the liquid coolant on the heat producing member, to flow into a delivery conduit. While in this conduit, the vapor mixes with liquid dielectric thereby decreasing the average density of the liquid vapor mixture. The pressure differences, coupled with this low mixture density cause the liquid dielectric to flow up the conduit and thereby be applied to the heat producing member. While this method is highly reliable due to the absence of moving parts, a considerable amount of power is required to vaporize the liquid dielectric in sufficient quantities such that an adequate amount of coolant is applied to the heat producing member.
Therefore, it is desirable, and it is the purpose of this invention, to provide a pump which has no moving parts and which also requires less input energy than prior art vapor pumps for vapor cooled electrical inductive apparatus.